Search

Introduction: In 2016, the Kenya National Immunization Technical Advisory Group requested additional programmatic and cost effectiveness data to inform the choice of strategy for a national influenza vaccination program among children aged 6-23 months of age. In response, we conducted an influenza vaccine demonstration project to compare the performance of a year-round versus campaign-mode vaccination strategy. Findings from this demonstration project will help identify essential learning lessons for a national program., Methods: We compared two vaccine delivery strategies: (i) a year-round vaccination strategy where influenza vaccines were administered throughout the year at health facilities. This strategy was implemented in Njoro sub-county in Nakuru (November 2019 to October 2021) and Jomvu sub-county in Mombasa (December 2019 to October 2021), (ii) a campaign-mode vaccination strategy where vaccines were available at health facilities over four months. This strategy was implemented in Nakuru North sub-county in Nakuru (June to September 2021) and Likoni sub-county in Mombasa (July to October 2021). We assessed differences in coverage, dropout rates, vaccine wastage, and operational needs., Results: We observed similar performance between strategies in coverage of the first dose of influenza vaccine (year-round strategy 59.7 %, campaign strategy 63.2 %). The coverage obtained in the year-round sub-counties was similar (Njoro 57.4 %; Jomvu 63.1 %); however, more marked differences between campaign sub-counties were observed (Nakuru North 73.4 %; Likoni 55.2 %). The campaign-mode strategy exceeded the cold chain capacity of participating health facilities, requiring thrice monthly instead of once monthly deliveries, and was associated with a two-fold increase in workload compared to the year-round strategy (168 vaccines administered per day in the campaign strategy versus 83 vaccines administered per day in the year-round strategy)., Conclusion: Although both strategies had similar coverage levels, the campaign-mode strategy was associated with considerable operational needs that could significantly impact the immunization program., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: SSC has since left the US CDC and is currently an employee of Sanofi Vaccines, Lyon, France., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Objectives: This study evaluated messages and communication approaches for maternal immunization uptake in Kenya. We identified persuasive communication aspects that would inform maternal immunization attitudes, intent, and vaccine uptake., Methods: We conducted a two-phased mixed methods study with pregnant women and their male partners in three regions of Kenya. Discussions were conducted in English and Swahili languages by trained focus group moderators. Baseline measures included a survey and discussions about potential messages and accompanying visuals. Follow-up focus groups with the same participants included a survey about previously discussed messages, visuals, and communication impressions. The second round of focus groups focused on message preferences developed from the first round, along with rank order discussion for final message selection. Following transcription of focus group discussions, we conducted analyses using NVivo software. Quantitative data analyses included frequencies, factor analyses, reliability assessment, regression modeling, and comparative assessment of rank order., Results: The sample (N = 118) included pregnant women (n = 91) and their partners (n = 27) from diverse Kenyan regions (Bondo/Lwak/Siaya, Mombasa, and Nairobi). A four-factor solution resulted from factor analyses that included subscales "positive ad attitudes" (n = 5 items, α = 0.82), "negative ad attitudes" (n = 4 items, α = 0.75), "ad indifference" (n = 2 items, α = 0.52), and "ad motivation" (n = 4 items, α = 0.71). Overall, the positive ad attitudes factor (β = 0.61, p = 0.03) was the only significant component in the overall model examining message selections (χ 2  = 262.87, p = 0.17). Among the tested concepts, we found that source and situational cues had a strong influence on women's attitude formation and intention to obtain recommended maternal vaccinations. With self-acknowledged variations in knowledge, participants were particularly attuned to images of relatable women, providers, and depictions in realistic or actual Kenyan clinical settings.(6)  = 262.87, p = 0.17). Among the tested concepts, we found that source and situational cues had a strong influence on women's attitude formation and intention to obtain recommended maternal vaccinations. With self-acknowledged variations in knowledge, participants were particularly attuned to images of relatable women, providers, and depictions in realistic or actual Kenyan clinical settings., Conclusions: The results indicated that positive attitudes were shaped by incorporating highly relatable factors in messages. Implications for subsequent campaigns and research directions are discussed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

Background: Healthcare workers (HCWs) are at high risk of exposure and transmission of infectious respiratory pathogens like influenza. Despite the potential benefits, safety and efficacy of influenza vaccination, vaccines are still underutilized in Africa, including among HCWs., Method: From May-June 2018, we conducted a cross-sectional, self-administered, written survey among HCWs from seven counties in Kenya and assessed their knowledge attitudes and perceptions towards pandemic influenza disease and vaccination. Using regression models, we assessed factors that were associated with the HCW's knowledge of pandemic influenza and vaccination., Results: A total of 2,035 HCWs, representing 49% of the targeted respondents from 35 health facilities, completed the question. Sixty eight percent of the HCWs had ever heard of pandemic influenza, and 80.0% of these were willing to receive pandemic influenza vaccine if it was available. On average, Kenyan HCWs correctly answered 55.0% (95% CI 54.0-55.9) of the questions about pandemic influenza and vaccination. Physicians (65.6%, 95% CI 62.5-68.7) and pharmacists (61.7%, 95% CI 57.9-65.5) scored higher compared to nurses (53.1%, 95% CI 51.7-54.5). HCWs with 5 or more years of work experience (55.8, 95% CI 54.5-57.0) had marginally higher knowledge scores compared to those with less experience (53.9%, 95% CI 52.5-55.3). Most participants who were willing to receive pandemic influenza vaccine did so to protect their relatives (88.7%) or patients (85.9%)., Conclusion: Our findings suggest moderate knowledge of pandemic influenza and vaccination by HCWs in Kenya, which varied by cadre and years of work experience. These findings highlight the need for continued in-service health education to increase the HCW's awareness and knowledge of pandemic influenza to increase acceptance of influenza vaccination in the case of a pandemic., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Ltd.)

Although influenza is primarily considered a respiratory infection and causes significant respiratory mortality, evidence suggests that influenza has an additional burden due to broader consequences of the illness. Some of these broader consequences include cardiovascular events, exacerbations of chronic underlying conditions, increased susceptibility to secondary bacterial infections, functional decline, and poor pregnancy outcomes, all of which may lead to an increased risk for hospitalization and death. Although it is methodologically difficult to measure these impacts, epidemiological and interventional study designs have evolved over recent decades to better take them into account. Recognizing these broader consequences of influenza virus infection is essential to determine the full burden of influenza among different subpopulations and the value of preventive approaches. In this review, we outline the main influenza complications and societal impacts beyond the classical respiratory symptoms of the disease., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: JN, SSC, SIS, and BTS are employees of Sanofi Pasteur. AEM has received honoraria for lectures or advisory boards from Sanofi Pasteur, Stendhal Pharma, Roche, and Pfizer. JEM has received honoraria for participation in advisory boards or lectures and related travel support from Sanofi, and participation in data monitoring boards or advisory boards for GSK, Pfizer, Merck, and Medicago. MCN has received honoraria for lectures or advisory boards from Sanofi Pasteur and Pfizer, and research grants from MedImmune. TW has received honoraria for lectures or advisory boards from MSD, Sanofi Pasteur, and Seqirus. HY has received investigator-initiated research funding from Sanofi Pasteur, GlaxoSmithKline, Yichang HEC Changjiang Pharmaceutical Company, and Roche (Shanghai)., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Influenza vaccination during pregnancy benefits mothers and children. Kenya and other low- and middle-income countries have no official influenza vaccination policies to date but are moving towards issuing such policies. Understanding determinants of influenza vaccine uptake during pregnancy in these settings is important to inform policy decisions and vaccination rollout., Methods: We interviewed a convenience sample of women at antenatal care facilities in four counties (Nairobi, Mombasa, Marsabit, Siaya) in Kenya. We described knowledge and attitudes regarding influenza vaccination and assessed factors associated with willingness to receive influenza vaccine., Results: We enrolled 507 pregnant women, median age was 26 years (range 15-43). Almost half (n = 240) had primary or no education. Overall, 369 (72.8%) women had heard of influenza. Among those, 288 (78.1%) believed that a pregnant woman would be protected if vaccinated, 252 (68.3%) thought it was safe to receive a vaccine while pregnant, and 223 (60.4%) believed a baby would be protected if mother was vaccinated. If given opportunity, 309 (83.7%) pregnant women were willing to receive the vaccine. Factors associated with willingness to receive influenza vaccine were mothers' belief in protective effect (OR 3.87; 95% CI 1.56, 9.59) and safety (OR 5.32; 95% CI 2.35, 12.01) of influenza vaccines during pregnancy., Conclusion: Approximately one third of pregnant women interviewed had never heard of influenza. Willingness to receive influenza vaccine was high among women who had heard about influenza. If the Kenyan government recommends influenza vaccine for pregnant women, mitigation of safety concerns and education on the benefits of vaccination could be the most effective strategies to improve vaccine acceptance., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Data on congenital cytomegalovirus (CMV) infection in Africa are limited., Objective: To describe the prevalence of congenital CMV infection in a population with high prevalence of maternal HIV and malaria infection in western Kenya., Study Design: We screened newborns for CMV by polymerase chain reaction assay of saliva swabs and dried blood spots (DBS), and assessed maternal CMV immunoglobulin G (IgG) status by testing serum eluted from newborn's DBS. We calculated adjusted prevalence ratios (aPRs) using log-binomial regression models., Results: Among 1066 mothers, 210 (19·7%) had HIV infection and 207 (19·4%) had malaria infection; 33 (3·1%) mothers had both. Maternal CMV IgG prevalence was 93·1% (95% confidence interval [CI]: 88·3%-96·0%). Among 1078 newborns (12 sets of twins), 39 (3·6%, 95% CI: 2·7-4·9%) were CMV positive. The prevalence of congenital CMV infection by maternal HIV and malaria infection status was 5·0% (95% CI: 2·7-9·2%) for HIV only, 5·1% (95% CI: 2·7-9·4%) for malaria only, 8·8 (95% CI: 3·1-23·0) for HIV and malaria co-infection, and 2·6% (95% CI: 1·7-4·1%) for none. Congenital CMV infection was independently associated with maternal HIV infection (aPR=2·1; 95% CI: 1·0-4·2), adjusting for maternal age, parity, and malaria infection., Conclusions: The prevalence of congenital CMV infection was higher than the 0·2-0·7% in developed countries. Maternal HIV infection may increase the risk of congenital CMV infection, but the role of maternal malaria on intrauterine transmission of CMV remains unclear., (Published by Elsevier B.V.)

Background: In 2014 the Kenya National Immunization Technical Advisory Group (KENITAG) was asked by the Ministry of Health to provide an evidence-based recommendation on whether the seasonal influenza vaccine should be introduced into the national immunization program (NIP)., Methods: We reviewed KENITAG manuals, reports and meeting minutes generated between June 2014 and June 2016 in order to describe the process KENITAG used in arriving at that recommendation and the challenges encountered., Results: KENITAG developed a recommendation framework to identify critical, important and non-critical data elements that would guide deliberations on the subject. Literature searches were conducted in several databases and the quality of scientific articles obtained was assessed using the Critical Appraisal Skills Programme tool. There were significant gaps in knowledge on the national burden of influenza disease among key risk groups, i.e., pregnant women, individuals with co-morbidities, the elderly and health care workers. Insufficient funding and limited work force hindered KENITAG activities. In 2016 KENITAG recommended introduction of the annual seasonal influenza vaccine among children 6 to 23 months of age. However, the recommendation was contingent on implementation of a pilot study to address gaps in local data on the socio-economic impact of influenza vaccination programs, strategies for vaccine delivery, and the impact of the vaccination program on the healthcare workforce and existing immunization program. KENITAG did not recommend the influenza vaccine for any other risk group due to lack of local burden of disease data., Conclusion: Local data are a critical element in NITAG deliberations, however, where local data and in particular burden of disease data are lacking, there is need to adopt scientifically acceptable methods of utilizing findings from other countries to inform local decisions in a manner that is valid and acceptable to decision makers., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective: To evaluate the cost-effectiveness of seasonal inactivated influenza vaccination among pregnant women using data from three recent influenza seasons in the United States., Design, Setting, and Participants: We developed a decision-analytic model following a cohort of 5.2 million pregnant women and their infants aged <6 months to evaluate the cost-effectiveness of vaccinating women against seasonal influenza during pregnancy from a societal perspective. The main outcome measures were quality-adjusted life-year (QALY) gained and cost-effectiveness ratios. Data sources included surveillance data, epidemiological studies, and published vaccine cost data. Sensitivity analyses were also performed. All costs and outcomes were discounted at 3% annually., Main Outcome Measures: Total costs (direct and indirect), effects (QALY gains, averted case numbers), and incremental cost-effectiveness of seasonal inactivated influenza vaccination among pregnant women (cost per QALY gained)., Results: Using a recent benchmark of 52.2% vaccination coverage among pregnant women, we studied a hypothetical cohort of 2,753,015 vaccinated pregnant women. With an estimated vaccine effectiveness of 73% among pregnant women and 63% among infants <6 months, QALY gains for each season were 305 (2010-2011), 123 (2011-2012), and 610 (2012-2013). Compared with no vaccination, seasonal influenza vaccination during pregnancy was cost-saving when using data from the 2010-2011 and 2012-2013 influenza seasons. The cost-effectiveness ratio was greater than $100,000/QALY with the 2011-2012 influenza season data, when CDC reported a low attack rate compared to other recent seasons., Conclusions: Influenza vaccination for pregnant women can reduce morbidity from influenza in both pregnant women and their infants aged <6 months. Seasonal influenza vaccination during pregnancy is cost-saving during moderate to severe influenza seasons., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for all persons in the United States aged ≥6 months. On June 25, 2014, ACIP preferentially recommended live attenuated influenza vaccine (LAIV) for healthy children aged 2-8 years. Little is known about national LAIV uptake. To determine uptake of LAIV relative to inactivated influenza vaccine, we analyzed vaccination records from six immunization information system sentinel sites (approximately 10% of US population). LAIV usage increased over time in all sites. Among children 2-8 years of age vaccinated for influenza, exclusive LAIV usage in the collective sentinel site area increased from 20.1% (2008-09 season) to 38.0% (2013-14). During 2013-14, at least half of vaccinated children received LAIV in Minnesota (50.0%) and North Dakota (55.5%). Increasing LAIV usage suggests formulation acceptability, and this preexisting trend offers a favorable context for implementation of ACIP's preferential recommendation., (Published by Elsevier Ltd.)

Children aged <9 years may require two doses of influenza vaccine to achieve an adequate immune response to protect against the disease. We analyzed data for >2 million children in each influenza season from 2007 to 2012 from eight Immunization Information System Sentinel Sites to assess trends in two-dose compliance. Compliance was calculated by influenza season, age group, and influenza vaccination history. Two-dose compliance increased from 49% to 60% among 6-23 month olds from 2007 to 2012; no increase was observed for 2-4 or 5-8 year olds. In each season, compliance was 3-12 times higher among 6-23 month olds compared to older children and was two times higher among influenza vaccine naïve children compared to previously vaccinated children. Improved messaging for providers and parents about the importance of the two-dose recommendation, about which children are eligible for two doses, and provider access to complete influenza vaccination histories for all children are needed., (Published by Elsevier Ltd.)

Background: Nosocomial spread of varicella-zoster virus (VZV) infection can cause severe disease among vulnerable patient-populations and healthcare personnel (HCP). Limited data are available on duration of varicella vaccine-induced protection among adults and to what extent cell-mediated immunity (CMI) and antibody avidity contribute to protection., Objective: Evaluate humoral and cell-mediated immune responses of HCP who received a 2-dose regimen of varicella vaccine, and observe the responses to a 3rd vaccine dose among HCP who were seronegative after vaccination., Study Design: A convenience sample of HCP with documented 2 doses of varicella vaccine was used to assess acquired VZV immune parameters (cytokine production, IgG avidity). HCP seronegative after 2 doses of vaccine were offered a third dose and evaluated further. Vaccine recipients' immune responses were compared with responses from persons with history of wild-type VZV infection., Results: The convenience sample consisted of 101 HCP with documented 2 doses of varicella vaccine; 12 (11.9%) were seronegative post-vaccination. 11.5% of 61 seropositive 2-dose recipients produced low avidity antibody, suggesting suboptimal response to vaccine. Seven 2-dose vaccinees who were VZV seronegative seroconverted after a third dose; however, 3/7 (42.9%) produced low avidity IgG. 142 persons with a history of varicella were all VZV IgG seropositive, and all had moderate to high avidity IgG., Conclusions: Measurements of serum IgG titers alone may not accurately reflect vaccine protection. Varicella vaccination of HCP remains important but further studies are needed to evaluate CMI and antibody avidity responses in HCP vaccinated with two doses of varicella vaccine., (Published by Elsevier B.V.)

The overall and indirect effects of immunizing school children with influenza A (H1N1) 2009 pandemic virus vaccine prior to and during the peak of virus circulation were evaluated on student and teacher school absenteeism. We used records collected from late 2009 through early 2010 from schools in four Maine counties. Mixed logistic regression models were used to estimate the daily association between school-level immunization coverage and absenteeism by level of influenza activity, after adjusting for the proportion of students receiving reduced-cost lunches, student minority status, absences adjacent to weekends and Thanksgiving, rural school location, and the circulation of other respiratory viruses. Increasing student immunization coverage was associated with reduced absenteeism during periods of high influenza activity. For example, as immunization coverage during the peak week of pandemic virus circulation increased from 38% to 69% (the 10th and 90th percentiles of observed coverage, respectively), relative reductions in daily absenteeism among all students, unimmunized students, and teachers were 8.2% (95% confidence interval [CI]: 6.5, 9.9), 5.7% (95% CI: 4.2, 7.3), and 8.7% (95% CI: 1.3, 16), respectively. Increased vaccination coverage among school-aged Maine children had modest overall and indirect effects on student and teacher absenteeism, despite vaccination occurring just prior and during peak pandemic virus circulation., (Published by Elsevier Ltd.)

The long-term duration of recombinant hepatitis B vaccine-induced immunity among persons vaccinated starting at birth is still not well understood. Waning of vaccine-induced immunity could leave young adults at risk of hepatitis B virus infection due to behavioral or occupational exposures. We followed a cohort of children immunized starting at birth with a 3-dose regimen of recombinant hepatitis B vaccine (5 mcg, 2.5 mcg, 2.5 mcg). They were challenged with a booster dose of the hepatitis B vaccine 10 and 15 years after vaccination to assess anamnestic response as a measure of persistence of protection. Among 108 participants who had lost protective antibody levels against hepatitis B, the majority (>70%) had an anamnestic response to the booster dose; response rates did not decline significantly between 10 and 15 years follow-up periods. A high antibody concentration following primary vaccination was independently associated with an anamnestic response later on in life. Nonetheless, ~20-30% of participants were unable to mount an immune response after boosting. Hepatitis B revaccination might be required for persons vaccinated starting at birth if opportunities for hepatitis B virus exposure exist. Future vaccine recommendations should be based on studies ascertaining protection against clinically significant disease., (Published by Elsevier Ltd.)

Background: Hepatitis B vaccination is recommended for patients on hemodialysis, however, seroprotection after a primary vaccine series is suboptimum. Limited data are available on the effect of revaccination of non-responders and on persistence of immunity in this population., Methods: Hepatitis B vaccine (40 μg/dose) was given to 77 susceptible patients on hemodialysis (0, 1, and 6 month schedule). Levels of hepatitis B surface antibody (anti-HBs) were tested ≥ 28 days after the third dose was administered, and non-responders revaccinated with an additional 3-dose series. Vaccine responders (anti-HBs ≥10 mIU/mL) were re-tested every 6 months and booster doses given as needed. Kaplan-Meier survival curve was used to estimate the probability of maintaining protective antibody level. Cox-proportional hazards models were used to assess the association between time to loss of protective antibody levels and certain explanatory variables., Results: Overall primary vaccine-induced response was 79.2% (95% CI 68.2%, 87.3%), including 49/77 (63.6%; 95% CI 51.8%, 74.7%) patients who received the initial primary hepatitis B vaccine series and 12/21 (57.1%; 95% CI 34.4%, 77.4%) non-responders who were revaccinated with an additional series. Among weak responders (anti-HBs level 10.0-99.9 mIU/mL), protective antibody levels persisted in 44% for 12 months post-vaccination; whereas among strong responders (anti-HBs level ≥100 mIU/mL), protective antibody levels persisted in 92% for 12 months, and 68% for 24 months post-vaccination. A weak post-vaccination response increased the risk of losing protective antibody levels (adjusted hazard ratio, 9.7; 95% confidence interval, 3.5-28.5; p<0.0001)., Conclusion: Revaccinating patients undergoing hemodialysis who do not respond to a primary vaccine series substantially increases the pool of protected patients. The threshold for defining hepatitis B vaccine-induced immunity should be revisited in this patient population to maximize the duration of protection., (Published by Elsevier Ltd.)

Background: Despite frequent use of self-reported information to determine pediatric influenza vaccination coverage, little data are available on the validity of parental reporting of their child's influenza vaccination status and on factors affecting its accuracy., Methods: We compared parent reported influenza vaccination of children to documented reports of vaccination collected from medical records (the criterion standard) among children aged 6-59 months who presented to selected hospitals, emergency departments, and clinics in three U.S. counties with acute respiratory illness during three influenza seasons (November through May of 2004-2007). Demographic and epidemiologic data were collected from chart reviews and parental surveys., Results: Among 3072 children aged 6-59 months, 47.5% were reported by the parent to have received influenza vaccine and 39.5% of children had medical record verification of influenza vaccination. Sensitivity and specificity of parental reporting was 92.1% and 82.3%, respectively, when compared to the immunization record. However, 17.7% of children whose parents reported vaccination had no influenza vaccination documented in their medical records, and this proportion was even higher at 28.6%, among children with an underlying high-risk medical condition. Greater reporting accuracy was associated with younger age of child (6-23 months vs. 24-59 months), white non-Hispanic race/ethnicity, having health insurance, and having a mother with a college education., Conclusions: Our findings indicate that although parental report of influenza vaccination is fairly reliable (∼76-96%), over reporting by parents often occurs and immunization record review remains the preferable method for determining vaccination status in children., (Published by Elsevier Ltd.)

To estimate the effectiveness of influenza vaccine against medical care visits for laboratory-confirmed influenza in young children we conducted a matched case-control study in children with acute respiratory illness or fever from 2005-2007. Influenza vaccine effectiveness (VE) was calculated using cases with laboratory-confirmed influenza and controls who tested negative for influenza. The effectiveness of influenza vaccine in fully vaccinated children 6-59 months of age was 56% (95% CI: 25%-74%); a significant VE was not found for partial vaccination., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

We analysed data from the 2009 National Immunization Survey to determine potential predictors of hepatitis A vaccination coverage among children aged 19-35 months. Overall national coverage was 75% for ≥1 dose. Residence in a state with hepatitis A vaccination recommendations prior to 2006, or in a metropolitan statistical area within such state, or being a minority child were among the variables independently associated with higher vaccination coverage. While hepatitis A vaccination coverage has improved since nationwide routine childhood vaccination began in 2006, coverage remains lower than that for other recommended childhood vaccines., (Published by Elsevier Ltd.)

Some hepatitis B vaccine booster studies have suggested waning of vaccine-induced immunity in adolescents vaccinated starting at birth. Those studies, however, used a pediatric formulation of the hepatitis B vaccine as a booster to detect anamnestic response. We compared adolescents boosted with an adult dose of hepatitis B vaccine with those boosted with a pediatric dose. Among adolescents who had lost protective antibody levels against hepatitis B, a higher proportion had an anamnestic response when boosted with the adult dose (60.0% vs. 43.8%). Thus, higher antigen concentrations may be required to elicit an adequate immune memory response. Despite improved anamnestic response, our study still raises concerns about whether children immunized in early infancy will remain protected from hepatitis B as they age into adulthood., ((c) 2010 Elsevier Ltd. All rights reserved.)

During the 2003-2004 influenza season, we conducted a case-control study of influenza vaccine effectiveness (VE) among Colorado residents aged 50-64 years. Cases (n=330) were identified from laboratory-confirmed influenza reports to the Colorado Department of Public Health and Environment (CDPHE). Controls (n=1055) were recruited by random-digit dial telephone survey. VE was 60% (43-72%) and 48% (21-66%) among those without and with high-risk medical conditions, respectively. VE was 90% (68-97%) and 36% (0-63%) against influenza-related hospitalization for persons without and with high-risk conditions, respectively.